Knowing
1km = 1000m
and conversely
0.001km = 1m
you can set up a ratio like so
66.0m/1000m = xkm/1km
66.0m(1km)/1000m = xkm
m cancel out and you are left with km
or conversely you can realize you are going from a smaller unit to a larger one so you just divide by 1000
if you were going the other way from larger to smaller units you would multiply by 1000